In these two two-cell mouse embryos, the surface of the embryos is outlined in orange, the DNA in the nucleus is indicated in blue and the activity of the LINE-1 gene is indicated via bright red spots.
Kelly Zimmerman holds her son Jaxton Wright at a parenting session at the Children's Health Center in Reading, Pa. The free program provides resources and social support to new parents in recovery from addiction, or who are otherwise vulnerable.
Natalie Piserchio for NPR
A serving of salmon contains about 600 IUs of vitamin D, researchers say, and a cup of fortified milk around 100. Cereals and juices are sometimes fortified, too. Check the labels, researchers say, and aim for 600 IUs daily, or 800 if you're older than 70.
Dorling Kindersley/Getty Images/Dorling Kindersley